Radiation risk real but misunderstood

The nuclear disaster following the Japanese earthquake and tsunami has Americans worried about the risks of exposure to radiation. The Food and Drug Administration has begun screening imported seafood after a number of nations banned Japanese imports following public concerns over radioactive materials entering the food supply, and talk about radiation preparedness in states with nuclear power plants has taken on a sudden urgency.

While environmental radiation exposure has captured the attention of the nation, the public faces the far more realistic prospect of exposure to medical radiation. Medical imaging — primarily x-ray and computed tomography (CT) — now constitutes the fastest-growing and, according to some experts, the single largest source of radiation exposure to many Americans, topping even naturally-occurring background sources.

Over the past decade, hospitals, mainly pediatric emergency rooms, have been exposing younger patients to ever increasing amounts of radiation. A study published this month by Cincinnati Children's Hospital surveying nationwide trends in pediatric radiation examined the use of CT scans over the past decade. Their study demonstrated a fivefold increase in CT scan use in children from 330,000 in 1995 to 1.65 million studies in 2008.

For perspective, a single abdominal CT scan provides a patient with the radiation equivalent of approximately 400 chest x-rays. Interaction of radiation particles with human DNA results in sometimes permanent genetic changes. These interactions are cumulative over time and disproportionately affect the sensitive tissues of younger people, resulting in deleterious effects on the body, such as cancer. Thus, the result of the over-radiating of the American public may not be known for years.

Someone who has had three CT scans of the abdomen has been exposed to the same amount of radiation as survivors standing within a few miles of the 1945 Hiroshima and Nagasaki atomic bomb blasts. While our ability to control radiation exposure from such external disasters is minimal, we can limit unnecessary exposure to medical radiation through education of the causes.

The reasons for these steady increases in medical imaging, and accompanying radiation, over the years are numerous, but can be viewed broadly in the following categories:

•Diagnostic laziness. Increases in studies ordered do not necessarily correspond to any increased complexity of medical diagnosis. Last year, a Johns Hopkins study demonstrated a three-fold increase in emergency room studies ordered nationwide over the past decade without any corresponding increase in diagnosis of life-threatening conditions. As pressures mount on physicians to see ever-increasing numbers of patients, traditional methods of patient assessment have gone by the wayside. Many doctors replace physical exams with diagnostic CT and MRI scans. Instead of laying their hands on the patient, physicians at the bedside have delegated diagnostic duties to other physicians, such as radiologists, who interpret these imaging studies. Worse yet, rising patient rolls from increasing health insurance coverage can only increase such dereliction of duty to the patient.

•Physician liability. This past February, the American Academy of Orthopedic Surgeons reported the results of a survey on the reasons physicians use to justify ordering imaging studies. Each order for an imaging study was tracked with a survey form documenting the reason for that order. About 20 percent of the surgeons in the survey ordered the study purely "for defensive reasons." Fear of a lawsuit in the current malpractice climate forces many physicians to resort to medical documentation through additional unnecessary imaging studies, including radiation-rich CT examinations.

•Physician reimbursement. Hit by cuts in reimbursement for patient visits, some physicians have made up lost revenue by resorting to self-referral of imaging cases to facilities in which they have ownership interest. The case of alleged unnecessary heart stent placement at St. Joseph Medical Center in Towson attracted significant national attention and U.S. Senate hearings stemming from the additional costs borne by consumers for each of those expensive stents. However, fewer recognized an additional byproduct of placing a stent — that is, increased radiation exposure, which is typically double that of a standard diagnostic heart exam.

In January, the Maryland Supreme Court upheld state rules prohibiting such conflicting interests. Federal laws currently do not go as far as Maryland statutes. Last week, a bill with similar provisions, the Integrity in Medicare Advanced Diagnostic Imaging Act of 2011, was introduced in the U.S. House. Similar bills filed in previous Congressional sessions have died after facing significant opposition from industry and medical alliances.

•Physician ignorance. Much of the information on radiation risk provided above is not standard knowledge, even among physicians. A 2004 study of emergency department doctors found less than 10 percent were aware that a patient's lifetime risk of cancer increased from a CT scan. Passage of an examination covering topics of radiation safety for board certification is only required of a single medical specialty — radiology. Training in radiation is not a requirement for graduation from U.S. medical schools and residency programs. Thus, the vast majority of physicians who order these tests have not undergone training and education about radiation risks despite the ability to order x-rays and CTs at the flick of a prescription pen.

When utilized properly, medical imaging offers high diagnostic accuracy with acceptable levels of radiation risk. The impetus for improvements in reducing the unnecessary radiation risk should be for the medical establishment to heal itself. However, absent meaningful change, increased public awareness of the potential for over-utilization should prompt patients to engage in discussions with their doctor when referred for these tests.

Dr. Sandeep Rao is an interventional radiology fellow at Johns Hopkins Hospital. His e-mail is srao28@jhmi.edu.

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